Acquisition of aerial imagery traces its history back to the Wright brothers, and is now commonly performed from satellite and space shuttle platforms, in addition to aircraft.
While the earliest aerial imagery relied on conventional film technology, a variety of electronic sensors are now more commonly used. Some collect image data corresponding to specific visible, UV or IR frequency spectra (e.g., the MultiSpectral Scanner and Thematic Mapper used by the Landsat satellites). Others use wide band sensors. Still others use radar or laser systems (sometimes stereo) to sense topological features in 3 dimensions. Other types of image collection rely on electro-optical panchromatic (grayscale), multi-spectral (less than 20 bands) and hyper-spectral (20 bands or more). Some satellites can even collect ribbon imagery (e.g., a raster-like, 1-dimensional terrestrial representation, which is pieced together with other such adjacent ribbons). Aerial imagery includes video as well as still imagery.
The quality of the imagery has also constantly improved. Some satellite systems are now capable of acquiring image and topological data having a resolution of less than a meter. Aircraft imagery, collected from lower altitudes, provides still greater resolution.
A huge quantity of aerial imagery is constantly being collected. Often the imagery includes miscellaneous objects such as cars or buildings. During image analysis each of these objects is—often manually—identified. Such processes are cumbersome and time consuming at best.
The present invention provides a mechanism for efficiently identifying physical objects depicted in aerial imagery. The physical objects are marked with machine-readable code prior to image capture. The machine-readable code persists in the imagery to aid identification of the marked object in the image. One application of these techniques is monitoring traffic from imagery captured by aerial platforms such as satellites, aircraft, elevated platforms, etc. Vehicles are marked on an outer surface with machine-readable code, which is preferably imperceptible to human observers but is detectable from optical scan data associated with the marked vehicle. The machine-readable code may include an identifier, which can uniquely identify the vehicle or link to associated information. In some implementations the machine-readable code includes a digital or steganographic watermark.
The foregoing and additional features and advantages of the present invention will be more readily apparent from the following detailed description with reference to the following figures.